Yesa you are right only one chip from alitech, but the maincode is diferentm but in the receivers that have the maincode 3606d and 3606h NOT WORKING the files 2.8.1 and 16-10 that working with maincode 3606q.
Regards
I think there are several manufacturers of receivers.
Perhaps they in factory flashing FW receivers
write the original version maincod in bootblock loader.
That is why the problems with running other FW.